Ductile corrosion-resistant alloy



United States Patent 3,311,470 DUCTILE CORROSION-RESISTANT ALLOY Dennis William Wakeman, Birmingham, Frank Grenville Haynes, Maidenhead, Keith J. Williams, Birmingham, Thomas E. Evans, Solihull, and William Barker,

Sutton Coidfield, England, assignors to The International Nickel Company, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 24, 1965, Ser. No. 442,495 Claims priority, application Great Britain, May 21, 1963,

20,204/63; Mar. 25, 1964, 12,656/ 64 19 Claims. (Cl. 75-170) This is a continuation-in-part of application Ser. No. 368,699, filed May 19, 1964.

The present invention relates to corrosion-resistant alloys and more particularly to nickel-base alloys characterized by an improved combination of characteristics including ductility and resistance to corrosion by acid media.

It is well known that alloys composed principally of nickel and containing silicon in amounts such as 8% to 11%, with or without other elements, possess good resistance to attack by acids and such alloys are therefore used, often in the cast form, for articles exposed to acid attack. A passivating silicate film forms on the surfaces of these alloys. It is also known that as the silicon content is increased, the resistance to corrosion is increased but the ductility is decreased. This loss of ductility results principally from the formation of brittle silicides, which occurs when the limit of solubility of silicon in nickel is exceeded.

Binary nickel-silicon alloys containing from 8% to 11% silicon, even when slowly cooled, present a microstructure of a massive alpha phase (the nickel-rich solid solution) and a eutectic of alpha and gamma phases, the composition of the gamma phase being Ni Si The beta phase, of composition Ni Si, can also exist. The beta phase is, however, rarely present in binary alloys since it has now been found that, contrary to some previously published information, the beta phase is formed as a result of a peritectoid reaction (reaction between two solid phases to form a third solid phase) occurring at about 1040 C. It appears that during normal casting operations, the rate of cooling is sufiiciently rapid to suppress this peritectoid reaction and the structure observed is the metastable alpha-gamma eutectic.

Although many attempts were made to overcome the foregoing difliculty of obtaining ductility in addition to corrosion resistance in nickel alloys of high silicon content and other difiiculties and disadvantages, none, as far as we are aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that a new nickel-base alloy is characterized by improved ductility and corrosion resistance.

It is an object of the present invention to provide a new nickel-base alloy characterized by an especially useful and improved combination of ductility and corrosion resistance.

Another object of the invention is to provide a process for improving the strength and ductility of a corrosionresistant nickel alloy of special composition.

The invention also contemplates providing a heat treated alloy characterized by a special microstructure and an improved combination of strength, ductility and corrosion resistance.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates a new nickel-silicon-titanium alloy possessing high corro- 3,3 l 1,47% Patented Mar. 28, 1967 sion resistance and good ductility and characterized by a microstructure comprising the beta phase Ni (Si, Ti). The alloy of the invention always contains at least about 1% and not more than 5% titanium and at least 7% silicon. The silicon content must be at least 7% since the corrosion resistance of similar alloys with less than 7% silicon is greatly inferior to that of alloys in accordance with the invention. Advantageously, the silicon content of the alloy of the invention is at least about 8% since when the silicon content is between 7% and 8% the corrosion resistance, though superior to that of binary alloys containing no beta phase, is not as good as that of alloys of the invention containing 8% or more silicon. The alloy of the invention can be a ternary alloy consisting essentially of nickel, silicon and titanium and it can also, in addition, contain any one or more of the elements copper, molybdenum and tungsten each in an amount not exceeding about 5% with the total of these elements not exceeding about 10%.

The present invention is particularly directed to an alloy containing about 8% to about 11% silicon, titanium in an amount of at least 1% and not more than 5% and, advantageously, about 2% to about 3.5%, up to 10% of metal from the group consisting of copper, molybdenum and tungsten in amounts up to 5% each with balance essentially nickel. All alloy percentages set forth herein are by weight. With a silicon content of about 10%, a preferred titanium content in an alloy of the invention is about 2.5%. In order to achieve both ductility and corrosion resistance, the alloy of the invention should contain not more than about 12% silicon, i.e., have a silicon content of 7% to about 12%. While it is also contemplated that useful alloys with up to 16% silicon, i.e., 7% to 16% silicon, can 'be provided in accordance with the invention, the alloy tends to be brittle when the silicon content is more than 12% owing to the introduction of primary gamma phase at about 12% silicon. Consequently, it is especially advantageous that the silicon con tent be 7% to 11%.

With up to 12% silicon, it is advantageous to correlate the silicon and titanium contents so that the sum of the silicon content plus one-half the titanium content is from about 9.5% to about 12.5% and it is even more advantageous that the silicon content plus one-half the titaniinn content be from about 11% to 12% with silicon from 7% to about 11%.

Titanium in the alloy of the invention mitigates the inherent brittleness of high-silicon, e.g., 8% or 11% silicon, nickel alloys and enhances the ductility of the alloy of the invention. Addition of titanium raises the peritectoid temperature and with about 2% titanium or more the peritectoid reaction is eliminated and the beta phase forms directly from the liquid. Also, the presence of titanium in the passivating silicate surface film which forms on alloys of the invention enhances the corrosion resistance of articles made of the alloy of the invention. Further, it has been found in accordance with the invention that titanium facilitates the formation of beta phase in the microstructure of the alloy in the las-cast condition and also that in order to be characterized by high corrosion resistance and ductility, the microstructure of the alloy when in use must comprise a high amount of beta phase, i.e., at least about beta phase or, advantageously, about or more beta phase. In addition to beta phase, the microstructure of the alloy can include the alpha or gamma phases, usually identifiable as the nickel-rich solid solution and the intermetallic compound Ni Si respectively, with titanium present in solution in the former and in solution in trace amounts in the latter. An alloy or article of the invention possesses an advantageous combination of strength, ductility and corrosion resistance when characterized by a microstructure containing at least about 90% beta phase, not more than about 10% alpha phase and/ or not more than about gamma phase.

The corrosive attack of concentrated sulfuric acid appears to be of a different kind from that of dilute sulfuric acid, i.e., acid of less than 40% concentration. Where particularly good corrosion resistance in dilute boiling sulfuric acid is required, best results are obtained when the alloy of the invention contains about 0.5% or more copper in addition to silicon and titanium, in aforedescribed amounts, with balance essentially nickel. Ductility of the alloy of the invention is decreased by increases in the copper content thereof and for obtaining a particularly good combination of ductility and corrosion resistance it is especially advantageous that all alloy in accordance with the invention contain about 1% to 2%, e.g., about 1%, copper. Good resistance to corrosive attack by concentrated sulfuric acid is obtained even when the alloy of the invention contains no copper.

Although the balance of the alloy of the invention is referred to as being essentially nickel, it is to be understood that minor amounts of impurities and other elements which are not harmful to the useful characteristics, especially corrosion resistance and ductility, of the alloy can also be present. Thus, the alloy can contain up to 3% iron, 1% manganese and 1 0% cobalt. However, the total of impurities must not exceed an amount such that the sum is equal to unity. Furthermore, it is important that the alloy of the invention must not contain more than about 0.01% of sulfur and 0.1% in total of carbon and nitrogen, since greater amounts of these last mentioned elements are highly detrimental to the ductility and extrusion characteristics of the alloy.

In carrying the invention into practice the ingredients of the alloy are melted and cast by using conventional furnace and ladle apparatus. Articles of the alloy of the invention can be cast to the shape required or, in apductility with little change in corrosion resistance is obtained by heat treating at about 1050" C. for at least four hours.

For the purpose of giving those skilled in the art a better understanding of the invention and a better appreciation of the advantages of the invention the following examples are given.

An alloy of the invention containing 7% to about 12% silicon, 1% to 5% titanium with the sum of the silicon content plus one-half of the titanium content equal to about 9.5% to about 12.5%, up to about 10% of metal from the group consisting of copper, molybdenum and tungsten in amounts up to 5% each with balance nickel, after undergoing the taforedescribed heat treatment at 1000 C. to 1100" C., is characterized by a microstructure comprising at least about 90% beta phase, not more than about 10% alpha phase and not more than about 5% gamma phase. The total amount of alpha phase in the alloy is substantially unchanged by the heat treatment; the beneficial effect of the heat treatment on ductility is due at least in part to a change in morphology of the aipha phase in the alpha plus beta eutectic.

The chemical compositions of fourteen examples of alloys in accordance with the present invention (Alloys 1 through 14) are set forth in Table I hereinafter. Alloys 1 through 14 were tested for resistance to corrosion in hot sulfuric acid of three different concentrations of aqueous solutions. The corrosion rates for the examples were determined and are set forth in Table I. In addition, Table I shows the corrosion rate of a 10% silicon, 3% copper, 87% nickel alloy (Alloy X) which differs from the alloy of the invention by not containing titanium as required by the invention. The corrosion rates set forth in Table I pertain to alloys in the as-cast or cast and heat-treated (1050 C. for 16 hours) condition, except for Alloys 8, 9, l0 and X which were tested in the as-extruded condition. There was found to be little difference between the corrosion resistance of each of the Alloys l7 and 11-14 in the as-cast condition and the same alloy in the cast and heat-treated condition.

TABLE I Alloy No.

Composition Corrosion Rate in H 804 Percent Percent Percent Other 257 75 90 1 Si Ti 0 propriate instances, the alloy can be extruded. The alloy of the invention, especially when the copper content thereof is not high, is characterized in the as-cast condition by superior ductility as compared to otherwise similar titanium-free alloys. The microstructure of the a loy in the as-cast condition is influenced by the cooling rate of the casting and will diifer somewhat according to the size and shape of the casting.

Substantial enhancement of both the ductility and the ultimate tensile strength of the alloy of the invention are concomitantly achieved by heat treating the alloy for about four hours to about 24 hours at about 1000 C. to about 1100" C., the longer time being needed at the lower temperature and vice versa. A particularly good effect on The test results set forth in the foregoing table show superior corrosion-resistant characteristics of examples of the alloy of the invention, with titanium, as compared with the corrosion rate of Alloy X, without titanium. It is clearly evident in view of the test results set forth in Table I that titanium is highly necessary as an ingredient in the alloy of the invention in order to obtain good corrosion resistance. In particular, it is to be noted that the examples having titanium contents in the advantageous range of 2% to 3.5% are characterized by advantageously low corrosion rates of less than 100 mgms./dm. /day (milligrams per square decirneter per day) in relatively high concentrations of acid such as 75% and sulfuric acid and that the examples containing copper in amounts up to 3% with titanium in the range 2% to 3.5 are characterized by advantageously low corrosion rates in dilute (25% concentration) boiling sulfuric acid and also in solutions of 75% and 90% sulfuric acid.

Examination of specimens subjected to attack by the three acid solutions referred to in Table I show that when present the alpha phase is selectively attacked and, accordingly, that the less alpha phase there is present the greater will be the corrosion resistance.

Tensile strengths and elongations pertaining to Alloys 1 through 9 and 11 through 14 of the invention and to Alloy X are set forth in Table II hereinafter. Results in Table II show that ternary alloys and copper-containing alloys of the invention possess substantially improved strength and ductility when in the heat treated condition obtained by heating for sixteen hours at 1050 C. or 1100 C. Alloy 11, which contains about silicon, 3% titanium, 1% copper and balance essentially nickel, is an example of an especially advantageous alloy of the invention and is shown in Tables I and II to possess an exceptionally good combination of high strength and corrosion resistance with good ductility in both the as-cast condition and the heated condition.

TABLE II Ultimate Tensile Strength (t.s.i.)

Condition Elongation,

Percent wan H CAJQWOEN GEUXOJR QIQQU! -p s ms r m ws s w T.s.i.=Long tons per squm'e inch. H.T.=Heat treated for 16 hours at indicated temperature.

The rate and the nature of the corrosive attack of boiling sulfuric acid on nickel-silicon alloys varies with the concentration of the acid and it has been found that the corrosive attack by boiling sulfuric acid of intermediate concentrations is of a different kind than the corrosive attack in dilute sulfuric acid or the corrosive attack in concentrated sulfuric acid. Thus, with regard to corrosion in boiling aqueous sulfuric acid solutions it is believed that in dilute acid solutions, e.g., 25% acid concentration (by weight), the rate of dissolution (corrosion rate) is primarily controlled by the evolution of hydrogen; in the intermediate range of 50% to 65 acid concentration the corrosion rate is primarily controlled by the formation of hydrogen sulfide and sulfur; and at high acid concentrations above 65% the corrosion rate is primarily controlled by the evolution of sulfur dioxide. When a dilute sulfuric acid solution is concentrated by boiling, the vessel in which the acid is contained is necessarily exposed to attacks of a different nature as the concentration increases. To be wholly satisfactory for use as the material of such a vessel, an alloy must have substantial resistance to corrosion by sulfuric acid of all concentrations.

It is pointed out hereinbefore that particularly good resistance to corrosion in boiling sulfuric acid of low concentrations up to 40% acid by weight is obtained when the alloy of the invention contains at least about 0.5% copper. Such nickel-silicon-titanium-copper alloys also have excellent resistance to corrosion by boiling sulfuric acid solutions of high concentrations greater than 65% and up to However, it has been found that nickelsilicon-titanium-copper alloys without molybdenum do not have satisfactory resistance to corrosion by boiling sulfuric acid of intermediate concentrations, e.g., sulfuric acid solutions containing about 50% to about 65% acid by weight.

It has been further discovered that when both copper and molybdenum are included in a nickel-silicon-titanium alloy in accordance with the invention, the corrosion resistance of the alloy to sulfuric acid of intermediate concentrations is greatly improved over that of similar alloys without molybdenum and, furthermore, the alloy is characterized by satisfactory impact resistance.

In order to obtain particularly good corrosion resistance in boiling aqueous sulfuric acid solutions, especially when the acid is of intermediate concentration of about 50% to 65%, the invention further provides an advantageous alloy composition containing at least 7% silicon, advantageously at least about 9% silicon, and about 1% to about 5% titanium with the silicon and titanium in amounts proportioned in accordance with the relationship Si+0.5(% Ti)=9.5 to 11.5

about 1% to about 4% copper, about 1% to about 4% molybdenum, advantageously about 2% to about 4% molybdenum, with the balance, except for impurities, being nickel.

In view of the relationship Si+0.5(% Ti) =9.5 to 11.5, it is apparent that the silicon content of the aforestated composition containing about 1% to about 5% titanium is not greater than about 11%.

Castings of the alloy of the invention are commonly used in the as-cast condition but can be heat treated to increase the ductility thereof by heat treatment comprising heating in the range of about 1000 C. to about 1100 C. for from about 4 to about 24 hours. The alloy of the invention is satisfactorily cooled from the heat treating temperature by air cooling.

A specific example (Alloy 15) of an alloy in accordance with the invention, contained about 9.3% silicon, about 2.8% titanium, about 3.1% copper, about 2.9% molybdenum, about 0.026% carbon, about 0.2% iron, less than 0.05% manganese, less than 0.06% aluminium and less than 0.01% chromium with the balance essentially nickel. Specimens of Alloy 15 exhibited good impact resistance by withstanding heavy blows of a hammer and thus were demonstrated to have impact resistant advantages over corrosion resistant iron-silicon alloys such as an iron-14.5% silicon alloy. Alloy 15 is an example of an especially advantageous alloy composition characterized by an excellent advantageously low corrosion rate not greater than about milligrams per square decimeter per day in boiling aqueous sulfuric acid at all concentrations up to 95%, which especially advantageous composition consists essentially of 9.2% to 10% silicon, 2.5% to 3% titanium, 2% to 3.5% copper, 2.5% to 3.5% molybdenum with balance essentially nickel. For good impact resistance it is advantageous that the amounts of copper and molybdenum in an alloy within the last stated composition be near the low end of the ranges for copper and molybdenum. Low corrosion rates of specimens of Alloy 15 in boiling sulfuric acid solutions are set forth in Table III. The specimens, which were in the as-cast condition, were suspended in the boiling acid for five periods of 24 hours each and the results set forth in Table III are averages of the corrosion rates during the last three 24 hour periods.

TAB LE III Sulfuric Acid Concentration (weight percent) Corrosion Rates (mgms/dmfi day) Comparative tests showed that in boiling sulfuric acid of intermediate concentrations the corrosion resistance of Alloy 15 was greatly superior to the corrosion resistance of an alloy containing 9.7% silicon, 2.8% titanium, 3% copper, less than 0.05% molybdenum and balance essentially nickel.

Another example (Alloy 16) of an alloy in accordance with the invention contained about 9.5% silicon, about 2.5% titanium, about 2.9% copper and about 3% molybdenum, with balance essentially nickel. Tests demonstrated that alloy 16 had low corrosion rates of 40 mgms./dm. day and mgms/dmF/day in boiling sulfuric acid solutions of 55% and 60% concentration, respectively. Also, Alloy 16 exhibited a high impact resistance (referred to herein as the energy absorbed in breaking an unnotched cylindrical bar about 2.25 inches long and about 0.45 inch in diameter) of 2.35 kilogram-meters (about 17 foot-pounds). The foregoing test results'pertaining to Alloy 16 were obtained on the alloy after heat treatment for 16 hours at 1050 C. and air-cooled.

Chemical compositions of additional examples of alloys in accordance with the invention, together with results of impact tests and corrosion tests thereof, are set forth in 40 Table IV.

pact resistance. For instance, a corrosion resistant ironsilicon alloy containing about 14.5% silicon is characterized by an unsatisfactory low impact resistance of 0.25 kg.-m. Impact test results set forth in Table IV show the alloy of the invention is characterized by satisfactory impact resistance that is clearly superior to the aforementioned low impact resistance of the iron-14.5% silicon alloy.

The present invention is applicable to the production of tough corrosion-resistant articles which are preferably produced as castings or by extrusion or other methods, with or without heat treatment. Useful articles which can be made of the alloy of the invention include pipe fittings, parts for pumps, stirrers, valves, reaction vessels, storage tanks and transfer lines for use in association with corroslve media including sulfuric acid. The alloy of the invention is also useful for corrosion-resistant pipe, tubing, rod, bar, plate and flanges.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. An alloy consisting essentially of 7% to about 16% silicon, 1% to about 5% titanium, up to about 5% copper, up to about 5% molybdenum and up to about 5% tungsten with the proviso that the total of copper, molybdenum and tungsten does not exceed 10% of the alloy, up to 3% iron, up to 1% manganese and up to 10% cobalt provided that the sum of the relationship does not exceed 1% and the balance essentially nickel.

2. An alloy as set forth in claim 1 containing 7% to about 12% silicon.

TABLE IV Composition Corrosion Rate Impact (mgmsJdmfi/day) Alicy Resistance,

No. kg.-m.

Percent Percent Percent Percent Percent 25% Ni Si Ti Cu Mo Bal. 9. 8 2 2. 9 2. 7 2. 4 130 213 120 Bal. 8. 7 3 3. 4 2. 9 4. 6 30 640 112 Bad. 9.7 2.6 2.9 3 0.7 32 7 Bal. 9. 4 2. 5 2.1 3 2. 2 66 37 Bel. 9. 2 3. 8 2. 1 2. 8 3. 5 52 Kg.-m.=Kilogram-metcrs. Corrosion Rate: Corrosion rate in milligrams per square decime-ter per indicated percentage concentrations by weight.

Impact test results set forth in Table IV were obtained with Alloys 17 through 21 in the condition obtained by heat treating the alloys at 1050 C. for 16 hours, followed by air-cooling. Corrosion test results in Table IV pertain to alloys as-cast.

Although some of the less advantageous alloys referred to in Table IV, e.g., Alloys 17 and 18, have rates of corrosion in 55% acid concentrations that are higher than optimum, the corrosion rates thereof are still so low that vessels of these alloys would have a useful life under some conditions.

It is well known that either the tensile elongation or the impact resistance of a material affords a measure of the handleability of a material, i.e., the ability of a material to resist damage during handling such as en countered in commercial production. Alloys made as castings can be usefully evaluated in practice by impact resistance tests since castings are often subject to impact, either unintentional or otherwise, during processing, transport, service, etc. A major disadvantage of some corrosion resistant alloys is brittleness, including very low imday in boiling sulfuric acid at 3. An alloy as set forth in claim 1 wherein the silicon and titanium are in proportions in accordance with the relationship Si-|-0.5(% Ti)=9.5 to 12.5

4. An alloy as set forth in claim 1 containing not more than 11% silicon and wherein the silicon and titanium are in proportions in accordance with the relationship 5. An alloy as set forth in claim 1 containing about 2% to about 3.5% titanium and wherein the silicon and titanium are in proportions in accordance with the relationship Si+0.5(% Ti)=1l to 12 6. An alloy as set forth in claim 1 containing 0.5% to about 5% copper and wherein the silicon and titanium are in proportions in accordance with the relationship Si+0.5(% Ti)=9.5 to 12.5

7. An alloy as set forth in claim 1 containing about 2% to about 3.5% titanium, about 1% to about 2% copper and wherein the silicon and titanium are in proportions in accordance with the relationship Si+0.5(% Ti)=1l to 12 8. An alloy as set forth in claim 1 containing about 10% silicon and about 3% titanium.

9. An alloy as set forth in claim 1 containing about 10% silicon, about 2% titanium and about 3% copper.

10. An alloy as set forth in claim 1 containing about 10% silicon, about 3% titanium and about 1% copper.

11. An alloy as set forth in claim 1 containing about 10% silicon, about 3% titanium and about 3% molybdenum.

1-2. An alloy as set forth in claim 1 containing about 10% silicon, about 3% titanium and about 3% tungsten.

13. An alloy as set forth in claim 1 containing about 1% to about 4% copper, about 1% to about 4% molybdenum and wherein the silicon and titanium are in proportions in accordance with the relationship Si+0.5(% Ti)=9.5 to 11.5

14. An alloy as set forth in claim .1 containing 9% to about 11% silicon, about 1% to about 4% copper, about 2% to about 4% molybdenum and wherein the silicon and titanium are in proportions in accordance with the relationship Si+0.5(% Ti)=9.5 to 11.5

15. An alloy as set forth in claim 1 containing 9.2% to 10% silicon, 2.5% to 3% titanium, 2% to 3.5% copper and 2.5% to 3.5% molybdenum.

16. An a'lloy as set forth in claim 1 which has the silicon and titanium in proportions in accordance with the relationship Si+0.5(% Ti)=9.5 to 12.5

and which is in the condition characterized by a microstructure comprising at least about 90% beta phase, not more than 10% alpha phase and not more than 5% gamma phase.

17. A vesesl for use in containing boiling sulfuric acid made of an alloy consisting of at least 7% silicon and about 1% to about 5% titanium with the silicon and titanium in amounts proportioned in accordance with the relationship Si+0.5(% Ti) :95 to 11.5

about 1% to about 4% copper, about 1% to about 4% molybdenum, up to 3% iron, up to 1% manganese and up to 10% cobalt provided that the sum of the relationship 10 0.33 Fe)+% Mn+0.1(% Co) does not exceed 1% and the balance essentially nickel and characterized by a microstructure comprising at least about 90% beta phase.

18. A vessel as set forth in claim 17 containing 9.2% to 10% silicon, 2.5% to 3% titanium, 2% to 3.5% copper and 2.5% to 3.5% molybdenum.

19. A process for improving the tensile strength of a ni'ckelcilicon-titanium alloy comprising heating an alloy consisting of 7% to about 12% silicon, 1% to about 5% titanium, up to about 5% copper, up to about 5% molyb- 'denum and up to about 5% tungsten with the proviso that the total of copper, molybdenum and tungsten does not exceed 10% of the alloy, up to 3% iron, up to 1% manganese and up to 10% cobalt provided that the sum of the relationship does not exceed 1% and the balance essentially nickel at a temperature of 1000" C. to about 1100 C. for about 4 hours to about 24 hours.

References Cited by the Examiner UNITED STATES PATENTS 1,076,438 10/1913 Marsh 170 1,556,776 10/ 1925 Flinterrnan 75-170 2,222,472 11/ 1940 Bishop 75170 FOREIGN PATENTS 14,046 11/ 1934 Australia.

References Cited by the Applicant UNITED STATES PATENTS 1,057,755 4/1913 Marsh. 1,769,229 7/ 1930 Mandell. 2,103,267 12/ 1937 Mandell. 2,222,471 11/ 1940 Bishop. 2,222,473 11/ 1940 Bishop.

FOREIGN PATENTS 580,686 9/ 1946 Great Britain.

OTHER REFERENCES Nickel Alloy Electrode Material for Spark Plugs, Chemical Abstracts, American Chemical Society, Nov. 27, 1961, vol. 55, No. 24, p 24510f.

DAVID L. RECK, Primary Examiner. R. O. DEAN, Assistant Examiner. 

0.33(% FE) + % MN + 0.1% CO)
 1. AN ALLOY CONSISTING ESSENTIALLY OF 7% TO ABOUT 16% SILICON, 1% TO ABOUT 5% TITANIUM, UP TO ABOUT 5% COPPER, UP TO ABOUT 5% MOLYBDENUM AND UP TO ABOUT 5% TUNGSTEN WITH THE PROVISO THAT THE TOTAL OF COPPER, MOLYBDENUM AND TUNGSTEN DOES NOT EXCEED 10% OF THE ALLOY, UP TO 3% IRON, UP TO 1% MANGANESE AND UP TO 10% COBALT PROVIDED THAT THE SUM OF THE RELATIONSHIP 